I have been working on this project over the past couple of weeks when I have free time but have not been posting updates. This is a general update which is why the title is different from the other posts regarding this project.
My boards from OSH Park arrived last week. I was able to populate them and test them out. Fortunately I did not make any errors on the PCB or schematic so they all worked as designed. There are a few things that I would change on a future version if I choose to make another version of the board.
- I would put the ICSP header on the bottom of the board so it does not stick out from the front. This would make it much easier to assemble and would make it possible to not have any exposed circuitry which may allow the device to be damaged from static electricity.
- I would move the resistors toward the bottom of the board if possible. It would allow the DHT11 sensor to stick out further from the case.
- I would also try to push the ATtiny85 a little further towards the bottom for the same reason as the resistors.
Currently I am looking to bit bang the I2C bus on the Raspberry Pi. I seem to have gotten around the clock stretching issue if there is only one device connected to the I2C bus but as soon as I add another device, the clock stretching becomes an issue again. I really wish that the Pi Foundation would work with Broadcom and fix the issue with the I2C bus.
Here are some pictures.
Bill of Materials (BOM)
Materials List (For One Sensor)
- QTY 1 – PCB (Source: OSH Park)
- QTY 2 – 3.5mm 4 Pole Audio Jack, J1 & J2 (Source: MCM Electronics NOTE: I ordered 27-9485 but received ones which look like 27-9487)
- QTY 1 – 2×3 Position Male Header 2.54mm Pitch, JP1 (Source: MCM Electronics NOTE: This is a 2×13 header. You will need to cut it for 2×3 header.)
- QTY 1 – T-1 3mm LED, LED1 (Source: MCM Electronics NOTE: May choose another color)
- QTY 1 – CDS Photoresistor Photoelectric 5549 GL5549, PH1 (Source: Ebay)
- QTY 2 – Resistor 1/4W 10K Ohm, R1 & R2 (Source: MCM Electronics)
- QTY 1 – Resistor 1/4W 220 Ohm, R3 (Source: MCM Electronics)
- QTY 1 – DHT11 Digital Temperature & Humidity Sensor Moudle, SE1 (Source: Ebay)
- QTY 1 – ATMEL ATtiny85, U1 (Source: Newark)
Materials List for Raspberry Pi Hat
- Qty 1 – Perfboard (Source: Adafruit)
- Qty 1 – GPIO Header for Raspberry Pi NOTE: The one you will need depends on which model of Raspberry Pi you are using. (Source: Adafruit 2×13 Header for original Raspberry Pi or 2×20 Header for newer Raspberry Pi)
- QTY 1 – 3.5mm 4 Pole Audio Jack (Source: MCM Electronics NOTE: I ordered 27-9485 but received ones which look like 27-9487)
- Optional items
I have added the source files for the Hardware and Software onto GitHub. I did this so the community may have access to the files and any updates to them. I mainly did it because I was having a hard time remembering which set of files I last worked with especially if a few days went by when I could not work on the project. I think this is a win-win for me and anyone interested in this project.
The files are located at https://github.com/TeelSys/TeelSys_THL. When you first go to the page, it may look like there are mo project files included in the project. If that is the case it is because I am still trying to get everything working properly before I commit code to the master branch. You will see a button with the text “Branch: master” and a downward arrow. Click that button and select another branch such as “dev”. You will then see the project files in their current state.
If you wish to contribute, add a comment here or if you can request through GitHub, do that. I will reply once I see the request but keep in mind that it may be a few days.